I use that kind of setup and just got a pump on the 14 of December. I was just firing and stirring it the temp dropped. I only used the heat at a very low setting. After about 45 minutes my temp might have dropped a degree or two is all. Firing and stirring or recirc using a pitcher for about 5 minutes brought me up to temp. The caveat that I would have is that my keggles are insulated with duct insulation and aluminum tape and then I throw a towel around the top when I'm letting the mash rest so my temps are probably more stable than a normal keggle.